Development of Oral Live Vaccine Prototypes Against Helicobacter Pylori Infections
Consorcio Tecnologico en Biomedicinaclinico-molecular S. A.
Mauricio Bulnes Bulnes Carrasco
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The infection by helicobacter pylori causes several diseases with different severity from a simple gastritis and going through chronic gastritis ulcer gastric atrophy MALT lymphoma and gastric carcinoma. Gastric cancer has been recognized as the 2nd most fatal form of cancer in the world. Of particular relevance there is a causative relationship between H. pylori and gastric cancer and a H. pylori vaccine would fill an urgent medical need. We are developing 2 prototypes of oral vaccines: one is based on the use of an attenuated bacterium and the other a safe probiotic both as live carriers of helicobacter pylori antigens to stimulate the immune system. It is well known that safety is a very important issue for drugs and in particular for vaccines. In this context probiotics are safer than attenuated bacterial strains. In addition attenuated strains present more side effects after vaccination. However attenuated strains induce a stronger response than probiotics so they could be more appropriate as live vaccines. Therefore we are currently working on both options so the best solution combining safety and efficacy will be chosen. The approach of using oral live vaccines has strong support. Firstly oral administration induces a general mucosal response at the gastrointestinal epithelia which is absent or reduced when intramuscular or subcutaneous via are used. Secondly oral administration is more acceptable to users rather than injections particularly when children need to be vaccinated. Finally in general injected substances such as medicines and vaccines compared to those orally given need a more strict manufacturing control because of toxicity and bacterial contamination and makes vaccine preparation a more expensive procedure. We have selected few particular antigens which are conserved in amino acid sequence and have wide distribution among H. pylori strains in order to assure a wide coverage of protection therefore our vaccines should be effective in a wider population. The oral live vaccine aims to offer a friendly presentation for users and should be safer than vaccines that directly uses the attenuated disease agent as a package of antigens to induce the immune system. In addition vaccines are usually prophylactic but in some cases they may be also therapeutic. At present we cannot anticipate if our product will present therapeutic properties but this aspect should be answered after some animal essays. If this feature is present in our prototypes it will add a higher value to these products.